Showing papers on "Differential scanning calorimetry published in 2007"
TL;DR: Both structural and thermal characteristics suggest that kraft pine lignin (L1) would be a better phenol (P) substitute in the synthesis of lign in-phenol-formaldehyde (LPF) resins, as it presents higher amounts of activated free ring positions, higher MW and higher thermal decomposition temperature.
933 citations
Journal Article•
TL;DR: In this article, B. mori silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity.
Abstract: We report a study of self-assembled beta-pleated sheets in B. mori silk fibroin films using thermal analysis and infrared spectroscopy. B. mori silk fibroin may stand as an exemplar of fibrous proteins containing crystalline beta-sheets. Materials were prepared from concentrated solutions (2−5 wt % fibroin in water) and then dried to achieve a less ordered state without beta-sheets. Crystallization of beta-pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally or by exposure to methanol. The fractions of secondary structural components including random coils, alpha-helices, beta-pleated sheets, turns, and side chains were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra. The silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity. The increment of the reversing heat capacity ΔCp0(Tg) at the glass transition fo...
837 citations
TL;DR: In this paper, the authors determined the proper amount of paraffin ( n -docosane) absorbed into expanded graphite (EG) to obtain form-stable composite as phase change material (PCM), examination of the influence of EG addition on the thermal conductivity using transient hot-wire method and investigation of latent heat thermal energy storage (LHTES) characteristics of Paraffin such as melting time, melting temperature and latent heat capacity using differential scanning calorimetry (DSC) technique.
793 citations
TL;DR: In this article, the authors show how carbon affects martensitic transformations in Ni-rich NiTi shape memory alloys and provide new experimental evidence for increasing temperature intervals between the start and the end of the martenitic transformations (from B2 to B19′) with increasing C content in as-cast and solution-annealed microstructures.
706 citations
TL;DR: This technique provides an efficient means of producing glassy materials that are low on the energy landscape and could affect technologies such as amorphous pharmaceuticals.
Abstract: Vapor deposition has been used to create glassy materials with extraordinary thermodynamic and kinetic stability and high density. For glasses prepared from indomethacin or 1,3-bis-(1-naphthyl)-5-(2-naphthyl)benzene, stability is optimized when deposition occurs on substrates at a temperature of 50 K below the conventional glass transition temperature. We attribute the substantial improvement in thermodynamic and kinetic properties to enhanced mobility within a few nanometers of the glass surface during deposition. This technique provides an efficient means of producing glassy materials that are low on the energy landscape and could affect technologies such as amorphous pharmaceuticals.
645 citations
TL;DR: In this article, the effect of molecular weight (MW) on the polymorphous crystallization and melting behavior of poly(l-lactide) were systemically studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), and time-resolved Fourier transform infrared (FTIR) spectroscopy.
Abstract: The effect of molecular weight (MW) on the polymorphous crystallization and melting behavior of poly(l-lactide) (PLLA) were systemically studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), and time-resolved Fourier transform infrared (FTIR) spectroscopy. It was found that the polymorphism of PLLA is not influenced much by MW, and the α‘- and α-form crystals are produced at low and high crystallization temperature (Tc), respectively, regardless of the MW. However, MW significantly affects the crystallization kinetics, and the crystallization rate reduces greatly with MW increasing. Moreover, the Tc- and MW-dependent melting behavior of PLLA was clarified with combining the DSC and FTIR results. It was found that the α‘- to α-crystalline phase transition occurs prior to the dominant melting in both the low- and high-MW PLLA crystallized at low Tc. Unlike the high-MW PLLA, in low-MW PLLA crystallized at low Tc, the α‘-form crystals only...
585 citations
TL;DR: In this article, a kind of spherical cellulose nanocrystals was prepared by hydrolysis of microcrystalline cellulose with mixed acid and two methods were used: diminishing the acid sulfate groups by desulfation and neutralizing them by using NaOH solution.
554 citations
TL;DR: In this article, the authors provide guidelines to adequately fit isothermal polymer crystallization kinetics data obtained by differential scanning calorimetry (DSC) employing the widely used Avrami equation.
546 citations
TL;DR: In this article, a combination of FTIR, elemental analysis, X-ray photoelectron spectroscopy, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) was used to reveal differences between Fe oleate structures for as-synthesized and postsynthesis treated (drying and extraction with polar solvents) compounds.
Abstract: The dependence of iron oxide nanoparticle formation on the structure and thermal properties of Fe oleate complexes has been studied using FTIR, elemental analysis, X-ray photoelectron spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM. The combination of FTIR, elemental analysis, and DSC allowed us to reveal differences between Fe oleate structures for as-synthesized and postsynthesis treated (drying and extraction with polar solvents) compounds. As-synthesized Fe oleate was found to contain a significant fraction of oleic acid, which works as a modifier altering the decomposition process and as an extra stabilizer during iron oxide nanoparticle formation. The thermal treatment of as-synthesized Fe oleate at 70 °C leads to removal of the crystal hydrate water and dissociation of oleic acid dimers, leading to a more thermally stable iron oleate complex whose final decomposition occurs at about 380 °C. Extraction of...
521 citations
TL;DR: A series of polyvinyl alcohol (PVA)/chitosan (CS) blend nanofibrous membranes with different weight ratio of PVA to CS were fabricated by electrospinning method as discussed by the authors.
486 citations
TL;DR: The results indicated that the cellulose nanocrystals could disperse in the WPU uniformly and resulted in an improvement of microphase separation between the soft and hard segments of the W PU matrix.
TL;DR: In this paper, the effect of processing temperature on the interfacial adhesion, mechanical properties and thermal stability of bio-flour-filled, polypropylene (PP) composites was examined as a function of five different maleic anhydride-grafted PP (MAPP) types.
Abstract: The effect of processing temperature on the interfacial adhesion, mechanical properties and thermal stability of bio-flour-filled, polypropylene (PP) composites was examined as a function of five different maleic anhydride-grafted PP (MAPP) types. To investigate the effect on the interfacial adhesion of the composites, the five MAPP types were subjected to characterization tests. The MAPP-treated composites with sufficient molecular weight and maleic anhydride (MA) graft (%) showed improved mechanical and thermal stability. The enhanced interfacial adhesion, and mechanical and thermal stability of the MAPP-treated composites was strongly dependent on the amount of MA graft (%) and the MAPP molecular weight. The morphological properties of the MAPP-treated composites showed strong bonding and a paucity of pulled-out traces from the matrix in the two phases. In addition, the improved interfacial adhesion of the MAPP-treated composites was confirmed by spectral analysis of the chemical structure using attenuated total reflectance (FTIR-ATR). The crystallinity of PP, MAPP, MAPP-treated composites and non-treated composites was investigated using wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC).
TL;DR: In this paper, the melting behavior of aluminum nanoparticles having an oxide passivation layer was examined using a differential scanning calorimetry (DSC) and the melting point depression, both corrected and uncorrected for the effects of the oxide shell, was linear with the reciprocal of particle radius.
TL;DR: A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) was performed using high-pressure differential scanning calorimetry (HP-DSC) measurements and in situ synchrotron powder X-ray diffraction (XRD) measurements along with kinetic investigations using a Sievert-type apparatus as discussed by the authors.
TL;DR: A series of highly soluble and fluorescent core-twisted perylene bisimide dyes (PBIs) 3 a-f with different substituents at the bay area were synthesized and fully characterized by (1)H NMR, UV/Vis spectroscopy, MS spectrometry, and elemental analysis.
Abstract: A series of highly soluble and fluorescent core-twisted perylene bisimide dyes (PBIs) 3 a-f with different substituents at the bay area (1,6,7,12 positions of the perylene core) were synthesized and fully characterized by (1)H NMR, UV/Vis spectroscopy, MS spectrometry, and elemental analysis. The pi-pi aggregation properties of these new functional dyes were investigated in detail both in solution and in condensed phase by UV/Vis and fluorescence spectroscopy, vapor pressure osmometry (VPO), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. Concentration-dependent UV/Vis measurements and VPO analysis revealed that these core-twisted pi-conjugated systems show distinct self-dimerization equilibria in apolar solvent methylcyclohexane (MCH) with dimerization constants between 1.3x10(4) and 30 M(-1). The photoluminescence spectra of the dimers of PBIs 3 a-f exhibit bathochromic shifts of quite different magnitude which could be attributed to different longitudinal or rotational offsets between the dyes as well as differences in the respective pi-pi stacking distance. In condensed state, quite a few of these PBIs form luminescent rectangular or hexagonal columnar liquid crystalline phases with low isotropization temperatures. The effects of the distortion of the pi systems on their pi-pi stacking and the optical properties of the resultant stacks in solution and in LC phases have been explored in detail. In one case (3 a) a particularly interesting phase change from crystalline into liquid crystalline could be observed upon annealing that was accompanied by a transformation from non-fluorescent H-type into strongly fluorescent J-type packing of the dyes.
TL;DR: Thermal analysis of the API-polymer-surfactant blends suggested that the surfactants caused solvation/plasticization, manifesting in reduction of the melting of API and T(m) of polymers and the combined T(g) of the solid dispersion formed from quench cooling.
TL;DR: In this paper, a novel citric acid (CA)-glycerol co-plasticized thermoplastic starch (CGTPS) was prepared by melt blending, which exhibits the special characters of partial esterification, low molecular weight and stronger interaction between starch and plasticizers.
TL;DR: In this paper, the structural transformations of Bioglass® during thermal treatments were studied via differential scanning calorimetry measurements in the range of 620 to 700 °C and temperature-time-transformation curves were established.
TL;DR: In this article, the melting and solidification processes of paraffin as a phase change material (PCM) in a tube in shell heat exchanger system were investigated. But the authors focused on the possibility of the heat transfer enhancement in the heat storage geometry, which is achieved by tilting the outer surface of the storage container.
TL;DR: In this paper, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) have been used to study S phase precipitation in an Al-4.2 Cu-1.5 Mg-0.08 Si (AA2324) (wt.%) alloy.
TL;DR: In this article, vanillin and β-cyclodextrin (β-CD) were prepared by the freeze-drying method and the formation of the inclusion complex was confirmed by differential scanning calorimetry (DSC).
TL;DR: In this article, phase transitions of amorphous sucrose and sucrose solutions (20-100% sucrose) were studied using differential scanning calorimetry, and related to viscosity and delayed ice formation.
Abstract: Summary
Phase transitions of amorphous sucrose and sucrose solutions (20–100% sucrose) were studied using differential scanning calorimetry, and related to viscosity and delayed ice formation. Glass transition temperature (Tg) was decreased by increasing water content. Ice formation and concurrent freeze concentration of the unfrozen solution increased apparent Tg. Tg could be predicted weight fractions and Tg values of components. Williams–Landel-Ferry (WLF) relation could be used to characterize temperature dependence of viscosity above Tg. Crystallization of water above Tg was time dependent, and annealing of solutions with less than 80% sucrose at –35°C led to a maximally freeze-concentrated state with onset of glass transition at –46°C, and onset of ice melting at -34°C. The state diagram established with experimental and predicted Tg values is useful for characterization of thermal phenomena and physical state at various water contents.
TL;DR: In this article, the phase change behavior of organic phase change materials (PCMs) in porous building materials was investigated using differential scanning calorimetry (DSC) and phase change composites.
TL;DR: The thermal stability of seven organically modified montmorillonites (organoclays) has been investigated using differential thermal analysis, differential scanning calorimetry, and thermogravimetry in conjunction with X-ray diffractometry as discussed by the authors.
TL;DR: In this article, the hydrogen bonding between poly(d,l-lactide) (PDLLA) and hydroxyapatite (HA) nanoparticles was investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopic (XPS).
Abstract: It was necessary to study the bonding mechanism of poly(d,l-lactide) (PDLLA) and hydroxyapatite (HA) nanoparticles because of their increasing application in medical fields. In this paper, hydrogen bonding between PDLLA and HA in PDLLA/HA nanocomposites was first investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Structural morphology and glass transition temperature (Tg) of the nanocomposites showed that there was a close interaction between polymer matrix and inorganic nanoparticls. The results from FTIR and XPS indicated that the hydrogen bonding between the CO in PDLLA and the surface POH groups of HA nanocrystalline was formed indeed. Shape memory properties were improved, which further implied the existence of hydrogen bonding in these nanocomposites. Thus, we designed a schematic model of the hydrogen bonding on the base of the experimental results. It can clearly ex...
TL;DR: SAS process could be a useful method for the preparation of the inclusion complex of drug with HP-beta-CD and its solubility, dissolution rate and hypolipidemic activity were significantly increased by complexation between SV and HP- beta-CD.
TL;DR: In this article, the enthalpy relaxation behavior of poly(l-lactide) (PLLA) below glass transition temperature (Tg) and its effects on the mechanical properties were studied using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile test.
Abstract: The enthalpy relaxation behavior of poly(l-lactide) (PLLA) below glass transition temperature (Tg) and its effects on the mechanical properties were studied using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile test. Both the enthalpy loss (δH) and peak endothermic temperature (Tp) in the glass transition region show a linear increase with the logarithm of aging time (ta). On the basis of DSC results, the kinetics of the enthalpy relaxation process were analyzed, and the kinetic parameters of PLLA were obtained: relaxation rate of enthalpy at 40 °C βH = 1.77 J g-1 per decade, and apparent activation energy Δh* = 1107 kJ mol-1. Besides, analysis on the kinetic of enthalpy relaxation for poly(dl-lactide) (PDLLA) shows that the Δh* value of PDLLA is similar to that of PLLA. Moreover, it was found that the strength and modulus of PLLA increase gradually; on the contrary, the toughness reduces dramatically during the physical aging. The yield strength and tensi...
TL;DR: The gelatinization characteristics of seven different food starches (regular corn, high-amylose corn, waxy corn, wheat, rice, potato, and tapioca) were investigated in this article.
TL;DR: In this article, the authors investigated the effects of inclusion of the liquid rubber phase in the transition phenomena that occur during the curing reaction, and the results obtained from the differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM).
TL;DR: A comparison of the values of the glass transition temperature (T g ) measured on cooling and the limiting temperature ðT 0f Þmeasured on heating as a function of cooling rate is performed for a polystyrene sample using both capillary dilatometry and differential scanning calorimetry (DSC) as discussed by the authors.
Abstract: A comparison of the values of the glass transition temperature (T g ) measured on cooling and the limiting fictive temperature ðT 0f Þmeasured on heating as a function of cooling rate is performed for a polystyrene sample using both capillary dilatometry and differentialscanning calorimetry (DSC). The results from both techniques indicate that T 0f is systematically lower than T g presumably due to thebreadth of the relaxation on cooling. The Tool–Narayanaswamy–Moynihan (TNM) model is used to fit the experimental data from dila-tometry and DSC in order to ascertain the origins of the higher value of T g compared to T 0f . 2007 Elsevier B.V. All rights reserved. PACS: 64.70.Pf; 65.60.+a; 81.70.Pg; 82.35.LrKeywords: Glass transition; Measurement techniques; Modeling and simulation; Polymers and organics; Calorimetry 1. IntroductionWhen a glass-forming material is cooled from the equi-librium liquid state, molecular mobility decreases withdecreasing temperature; at some point, the time scale forconformational changes becomes comparable to the timescale of cooling and the material deviates from the liquidline and begins to form a glass. The glass transition is,hence, a kinetic rather than a thermodynamic transitionand depends on cooling rate [1,2]. The glass transition tem-perature (T